SEBA Class 9 Science Important Chapter 12 Sound

SEBA Class 9 Science Important Chapter 12 Sound Solutions English Medium As Per SEBA New Syllabus to each chapter is provided in the list so that you can easily browse through different chapters SEBA Class 9 General Science Additional Solutions and select need one. NCERT Important Solutions For Class 9 General Science Download PDF. Important Notes for Class 9 Science.

SEBA Class 9 Science Important Chapter 12 Sound

Also, you can read the NCERT book online in these sections Solutions by Expert Teachers as per Central Board of Secondary Education (CBSE) Book guidelines. Assam SEBA Board Class 9 Science Additional Question Answer are part of All Subject Solutions. Here we have given CBSE Class 9 Science Important Notes for All Chapters, You can practice these here.

Sound

Chapter: 12

IMPORTANT QUESTION ANSWER

Answer the Following Question:

1. What is the SI unit of frequency?

Ans: Hertz (Hz).

2. What is required for the propagation of sound?

Ans: A material medium (solid, liquid or gas).

3. What is the audible range of human hearing?

Ans: 20 Hz to 20,000 Hz.

4. Name the waves with frequencies below 20 Hz.

Ans: Infrasonic waves. 

5. Name one device used to hear heartbeats using reflection of sound.

Ans: Stethoscope.

6. Which property of sound helps us distinguish different voices?

Ans: Quality or timber.

7. What is sound? How is it produced?

Ans:Sound is a form of energy that produces the sensation of hearing in our ears.

It is produced when an object vibrates, causing the surrounding medium to vibrate. These vibrations travel in the form of waves to our ears and are perceived as sound. 

Example: A tuning fork produces sound when struck and vibrates.

8. Why is sound considered a mechanical wave?

Ans: Sound requires a material medium (solid, liquid, or gas) to travel, and cannot propagate through a vacuum.

It transfers energy through the vibrations of particles in the medium, not through particle motion. Hence, it is called a mechanical wave.

9. Why do we hear thunder after seeing lightning?

Ans: Light travels much faster than sound. So, even though thunder and lightning occur at the same time, light reaches our eyes before the sound reaches our ears.

10. What is reverberation? How can it be reduced in auditoriums?

Ans: Reverberation is the persistence of sound due to repeated reflections from walls and ceilings.It can be reduced by using sound-absorbing materials like curtains, fibreboards, carpets, and rough surfaces in the auditorium.

11. What is ultrasound? Name two applications of ultrasound.

Ans: Ultrasound refers to sound waves with frequency greater than 20,000 Hz.

Applications:

(i) Used in medical imaging (e.g., ultrasonography).

(ii) Used to detect defects or cracks in metal blocks.

12. Explain the working of a hearing aid.

Ans: A hearing aid is a battery-powered electronic device. It receives sound via a microphone, converts it to electrical signals, amplifies it, and then sends it to a speaker, which converts it back to sound for the user to hear clearly.

13. A sound wave has a frequency of 2000 Hz and wavelength of 0.35 m. Calculate its speed.

Ans: Given:

Frequency (ν) = 2000 Hz

Wavelength (λ) = 0.35 m

Speed (v) = λ × ν = 0.35 × 2000 = 700 m/s.

14. What are the characteristics of a sound wave?

Ans: Main characteristics of a sound wave are:

(i) Wavelength (λ) – Distance between two compressions or rarefactions.

(ii) Frequency (ν) – Number of oscillations per second.

(iii) Amplitude (A) – Maximum displacement from mean position.

(iv) Time period (T) – Time taken for one complete oscillation.

(v) Speed (v) – Rate of propagation in a medium.

15. What is the role of soundboards in large halls or auditoriums?

Ans: Soundboards are used to reflect sound uniformly so that it reaches all parts of the hall. They prevent sound loss and reduce reverberation by redirecting sound effectively.